1. Field of the Invention
This invention relates to a method of and an apparatus for separating water and agglomerate of colloidal particles in an aqueous colloidal solution with colloidal particles dispersed in liquid mainly composed of water, such as alkali washing liquid with oil dispersed in water in the form of oil-drop-in-water emulsified particles in water. By the term "colloidal particles" is meant either or both of liquid particles (i.e., emulsified particles) and solid particles (i.e., hydrophobic colloidal particles). By the term "agglomeration" is meant gathering of particles into a greater particle. Where colloidal particles are dispersed in an aqueous solution, by the term "separation to water and colloidal particles" is meant separation to aqueous solution and agglomerate of colloidal particles.
2. Prior Art
It is well known in the art that a system in which water is dispersed in oil can be separated into water and oil with application of a voltage to the system, as disclosed in, for instance, U.S. Pat. Nos. 4,391,698 and 4,409,078. These prior art literatures also disclose a technique of applying an AC voltage and also that efficient separation is obtainable with application of a voltage of 2 to 100 KV at a frequency of 60 to 1,500 Hz. Similar techniques are also disclosed in Japanese Laid-Open Patent Publication No. 58-156309. In this technique, commercial power of 60 to 120 V (at 50 to 60 Hz) is applied to colloidal solution.
The above disclosed techniques are for processing systems in which water is dispersed in solution mainly composed of oil. Oil has low electric conductivity compared to water, and current caused through oil is low even by applying comparatively high voltage. Besides, there is no problem of electrolysis of oil content. Thus, efficient separation is obtainable by application of comparatively high voltage.
However, where oil or the like is dispersed in water, current is readily caused because water has high electric conductivity compared to oil. Therefore, if the voltage applied is increased to promote the separation, a high voltage high current is caused to result in shortage of the capacity of the power source. Besides, because of the high current caused, electrolysis of water takes place. When the electrolysis of water occurs, colloidal particles of oil or the like are oxidized by oxygen that is generated, so that they can not be recovered in a satisfactory state. At present, therefore, a method of separation of an aqueous colloidal solution to water and colloidal agglomerate with voltage application does not provide for satisfactory results.